1. Field of the Invention
The present invention relates to a case image search apparatus and system, particularly to a technology for using a feature value extracted from a query image to search for a case image similar to the query image.
2. Description of the Related Art
A method for searching for a three-dimensional model has been proposed (Japanese Patent Application Laid-Open No. 2004-164503). The method includes the steps of extracting a feature value (first feature value) from a two-dimensional image that will be a search key, generating a plurality of two-dimensional images by viewing a three-dimensional model to be searched for from different points of view, extracting a feature value (second feature value) from each of the plurality of two-dimensional images, using the first and second feature values to carry out similarity searching, and searching for a three-dimensional model similar to the search key.
An apparatus for searching for a similar image has also been proposed (Japanese Patent Application Laid-Open No. 2001-155019). The apparatus sets part of a three-dimensional image to be diagnosed as a region of interest, extracts a feature value from the region of interest, compares the extracted feature value with feature values of images in a database to calculate similarities, and selects similar images from the database based on the calculated similarities in descending order of similarity.
Further, an apparatus for displaying a three-dimensional image has been proposed (Japanese Patent Application Laid-Open No. 2001-101449). The apparatus sets a plane in an image three-dimensional voxel space with reference to a three-dimensional image displayed after arbitrarily rotated and moved, and uses the pixel values of the voxels that interest the plane to create an MPR image. It is therefore possible to easily display an MPR image arbitrarily angled and positioned and intuitively understand the positional relationship between the MPR image and the three-dimensional image.
The three-dimensional model search method described in Japanese Patent Application Laid-Open No. 2004-164503 requires preparing a plurality of second feature values used for searching for one three-dimensional model in advance (feature values extracted from a plurality of two-dimensional images obtained by viewing a three-dimensional model from different points of view). Therefore, in particular, when the direction of the two-dimensional image that will be the search key (the direction of the line of sight) is not established, it is necessary to prepare the second feature values for all possible directions of the line of sight. Further, when a large number of three-dimensional models will be searched for, it is difficult to prepare the second feature values.
The similar image detection apparatus descried in Japanese Patent Application Laid-Open No. 2001-155019 cannot search a database for a two-dimensional image similar to a reference two-dimensional image or a three-dimensional image containing the reference two-dimensional image therein.
The three-dimensional image display apparatus described in Japanese Patent Application Laid-Open No. 2001-101449 is not designed to search an image database for an image or display a searched image, and hence no screen interface is considered, for example, for searching for a similar case.